1. Field of the Invention
The present invention relates to apparatus for the attitude control of a plate-form body. More particularly, the present invention relates to the attitude control apparatus of wafer or mask used for the precision alignment of a photo mask with a semiconductor substrate surface in making semiconductor elements.
2. Description of the Prior Art
In making semiconductor elements a pattern on a photo mask is printed on a wafer by use of an exposure apparatus. As a kind of such exposure apparatus there is known the so-called proximity exposure apparatus in which the photo mask and the wafer are held in close proximity to each other. In the case of proximity exposure apparatus a particularly high precision is required in the alignment of mask with wafer. Man has to carry out an alignment work before every exposure. In brief, the alignment work involves the following operations:
(1) To align the alignment mark on the mask with the alignment mark on the wafer. At this step of operation, mask and/or wafer must be moved in the directions of X-Y axes and also rotated in the direction of .theta..
(2) To bring the mask and wafer into the positions in parallel with each other. For this operation the mask and/or wafer are required to be inclinable in any direction without losing the alignment of the alignment marks obtained at (1). In order to keep the established alignment of the alignment marks, the displacement of mask and/or wafer in X-Y directions must be minimized at this step of operation (2).
(3) To adjust the gap size between mask and wafer to a predetermined value. For this operation the mask and/or wafer are required to be movable in the fashion of parallel displacement in the direction of Z-axis perpendicular to the plane containing X-Y axes.
When a proximity exposure apparatus is used, the alignment operations described above are required in principle. The adjustments of parallelism and gap size between mask and wafer are very important in particular when an X-ray exposure apparatus is used. In the X-ray exposure apparatus X-rays are emitted toward a definite size of target and a mask pattern is exposed onto a wafer by the X-rays. In this case, the alignment accuracy in X-Y directions is greatly affected by the error in adjustment of gap size between mask and wafer. Therefore, the gap size as well as the parallelism between mask and wafer should be controlled very very precisely.
These requirements may be satisfied by uniting two mechanisms, for example, for above operations (1) and (2) together. However, it will render the structure of the apparatus very complicated as a whole.